The serum gastrin level test is employed to diagnose a range of gastric disorders by measuring gastrin, a peptide hormone that targets the gastric fundus and cardiac regions. Gastrin promotes gastric mucosal growth, enhances motility, and stimulates hydrochloric acid secretion. Healthcare professionals use this test to diagnose gastrinoma, Zollinger-Ellison syndrome, gastric and duodenal ulcers, and pernicious anemia.